The invention relates to a method in a reel-up used for the reeling up of a paper web or the like. Furthermore, the invention relates to a center drive device of a reel-up for implementing the method.
A web that is several meters wide and comes directly from a paper machine or a finishing apparatus connected thereto continuously in an on-line type manner is reeled in a so-called reel-up to form successive machine reels around reeling cores, so-called reel spools. These large machine reels, which substantially comply with the production width of paper, function as kind of intermediate storages for the paper web between off-line type finishing devices. In front of off-line type finishing devices, such as coating machines for paper web, a so-called unwinder is used to guide the web reeled up in the preceding reeling device from successive reels to said finishing apparatus. Said preceding reeling device can be a so-called re-reeler in which the machine reel reeled in a reel-up of a paper machine is unwound in the unwinder of the intermediate reel-up, and it is reeled up again in the reel-up of the intermediate reel-up to form a reel that is suitable for the finishing process in question. In the end of an off-line finishing apparatus, such as an off-line coating machine, there is typically yet another reel-up in which the paper web coming from said apparatus is reeled around the reeling core again to form a machine reel.
There are several solutions of different types for reel-ups, including the so-called center-drive assisted reel-up which is the reel-up type generally in use at present. This reel-up type utilizes a reeling cylinder equipped with a center drive as well as a machine reel that is in nip contact with the same in the reeling station. The paper web is guided on the machine reel via a nip formed between the reeling cylinder and the machine reel that is being formed. In center-drive assisted reel-ups the reeling core of the machine reel is also provided with a center drive of its own to improve the control of the reeling process. In a solution that is generally used in center-drive assisted reel-ups, the reeling cylinder has a stationary position and thus the center-driven reeling core of the machine reel moves on its support in relation to said reeling cylinder at different stages of the reeling up process and/or as the amount of web around the reeling core grows.
The present invention relates especially to reel-ups of the above kind in which the reeling core of the machine reel that is being formed is arranged to move during the reeling up process as the center drive of the machine reel is coupled to said reeling core.
The book by Mikko Jokio: Papermaking Part 3 Finishing, published by Fapet Oy, ISBN 952-5216-10-1, 1999, pp. 162 to 163, discloses a reel-up based on the use of a stationary reeling cylinder. In the following, the operating principle of said reel-up will be discussed briefly.
According to the facts stated in the above-mentioned reference, the reeling up to a new empty reeling core is started in a so-called primary reeling device. First, the primary reeling device receives the empty reeling core from a storage on end support on arms or the like that function as gripping means. Said storage is located above the reeling cylinder and the paper web, in an area that is within reach of the primary reeling device. The primary reeling device contains a so-called primary center drive that is coupled to a power transmission connection with the other end of the reeling core. By means of the primary center drive the empty reeling core is accelerated to a speed corresponding to the speed of the reeling cylinder and the paper web, whereafter the reeling core is transferred closer to the reeling cylinder, and further in nip contact with the reeling cylinder, at the same time performing the threading of the paper web to said reeling core at a suitable stage. The aforementioned threading and thus the change of the reeling up process to a new reeling core are usually conducted in a so-called flying change without reducing the speed of the paper web entering the reel-up during the change. The reeling up to the reeling core located in the primary reeling device continues now by means of the primary center drive until the preceding full machine reel has been transferred out of the way. At a suitable stage the primary reeling device lowers the reeling core that is under its control on end support on rails, on carriages moving on the rails, or on a corresponding support, the structures implementing the support being dimensioned to support the eventual weight of the full machine reel that is being formed. The reeling core and the new machine reel formed thereon are transferred away from the control of the primary reeling device by changing the so-called secondary center drive released from the finished machine reel to the free end of the reeling core, and by releasing the primary center drive of the primary reeling device from the other end. During this change the torque necessary for rotating the reeling core is ramped, i.e. changed gradually from said primary center drive to said secondary center drive and the reeling up process continues during said change without interruptions. When the primary reeling device has become free, the primary reeling device returns to retrieve the next empty reeling core from the storage for the next change.
The above-mentioned primary center drive and secondary center drive are both composed of the following main components: the actual drive motor, a gear system transforming the transmission ratio of the rotating speed of the motor into a suitable level, as well as a coupling mechanism engaging to the end of the reeling core. In solutions of prior art the aforementioned components of the primary center drive are fixed to the primary reeling device itself, and thus they can move along with the reeling core located in the primary reeling device when the primary reeling device turns from one position to another in the different operating stages of the reeling up process. In solutions of prior art the drive motor, the gear system and the coupling mechanism of the secondary center drive are also fixed on a moving base or the like, said base moving along with the machine reel as the diameter of the machine reel grows, and the reeling core moves in relation to the stationary reeling cylinder. U.S. Pat. No. 5,375,790 discloses in more detail a solution in which the unit composed of the drive motor, the gear system and the coupling mechanism of the secondary center drive moves on the side of the rail supporting the other end of the reel spool, thus following the movement of the reel spool and its reeling core.
One way of connecting the drive motor to the end of the reel spool is also disclosed in the U.S. Pat. No. 5,069,394.
The weight of the drive motor of the center drive is typically in the order of 2,000 kg, and the weight of the gear system coupled to the drive motor in the order of 1,200 kg. In order to load the structures of the reel-up symmetrically, counterweights are used in the opposite end of the reeling core to balance the weight of the drive motor and gear system that are coupled to the end of the reeling core and move along with the reeling core. When the motor, the gear system and the counterweights as well as the structures necessary for moving said components are taken into account, the total weight of the components and structures that need to be lifted up is in the order of 10,000 kg per one center drive.
In such reel-ups in which the primary and/or secondary drives are moved along with the reeling core, it is thus in solutions of prior art necessary to implement quite strong supporting and moving structures merely for the components relating to the center drive. This means that the implementation of said structures causes significant costs, because both the amount of work required therein and the amount of steel used as raw material are quite considerable.
In order to maintain the weight as low as possible the motors and gear systems used in the center drives must be selected by taking account especially the weight and size of the same, wherein the use of alternative and less expensive components is limited in solutions of prior art.
One harmful result of the great weight of the components of the center drives and the supporting structures of the same in reel-ups is still the fact that especially in the primary reeling device of the reel-up the weight of the components moving along with the primary reeling device of the primary center drive can complicate the accurate control of the nip load i.e. linear load between the reel that is being formed and the reeling cylinder. The nip load is an essential parameter used in the reeling up process, by means of which it is possible to affect the quality of the machine reel that is being formed and the preservation of the properties of the reeled-up paper web.